1 /* 2 * Copyright (c) 2016, Intel Corporation 3 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com> 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License 7 * as published by the Free Software Foundation; either version 8 * 2 of the License, or (at your option) any later version. 9 */ 10 #include <linux/kernel.h> 11 #include <linux/export.h> 12 #include <linux/err.h> 13 #include <linux/string.h> 14 #include <crypto/dh.h> 15 #include <crypto/kpp.h> 16 17 #define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 4 * sizeof(int)) 18 19 static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size) 20 { 21 if (!dst || size > end - dst) 22 return NULL; 23 memcpy(dst, src, size); 24 return dst + size; 25 } 26 27 static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size) 28 { 29 memcpy(dst, src, size); 30 return src + size; 31 } 32 33 static inline unsigned int dh_data_size(const struct dh *p) 34 { 35 return p->key_size + p->p_size + p->q_size + p->g_size; 36 } 37 38 unsigned int crypto_dh_key_len(const struct dh *p) 39 { 40 return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p); 41 } 42 EXPORT_SYMBOL_GPL(crypto_dh_key_len); 43 44 int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params) 45 { 46 u8 *ptr = buf; 47 u8 * const end = ptr + len; 48 struct kpp_secret secret = { 49 .type = CRYPTO_KPP_SECRET_TYPE_DH, 50 .len = len 51 }; 52 53 if (unlikely(!len)) 54 return -EINVAL; 55 56 ptr = dh_pack_data(ptr, end, &secret, sizeof(secret)); 57 ptr = dh_pack_data(ptr, end, ¶ms->key_size, 58 sizeof(params->key_size)); 59 ptr = dh_pack_data(ptr, end, ¶ms->p_size, sizeof(params->p_size)); 60 ptr = dh_pack_data(ptr, end, ¶ms->q_size, sizeof(params->q_size)); 61 ptr = dh_pack_data(ptr, end, ¶ms->g_size, sizeof(params->g_size)); 62 ptr = dh_pack_data(ptr, end, params->key, params->key_size); 63 ptr = dh_pack_data(ptr, end, params->p, params->p_size); 64 ptr = dh_pack_data(ptr, end, params->q, params->q_size); 65 ptr = dh_pack_data(ptr, end, params->g, params->g_size); 66 if (ptr != end) 67 return -EINVAL; 68 return 0; 69 } 70 EXPORT_SYMBOL_GPL(crypto_dh_encode_key); 71 72 int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params) 73 { 74 const u8 *ptr = buf; 75 struct kpp_secret secret; 76 77 if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE)) 78 return -EINVAL; 79 80 ptr = dh_unpack_data(&secret, ptr, sizeof(secret)); 81 if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH) 82 return -EINVAL; 83 84 ptr = dh_unpack_data(¶ms->key_size, ptr, sizeof(params->key_size)); 85 ptr = dh_unpack_data(¶ms->p_size, ptr, sizeof(params->p_size)); 86 ptr = dh_unpack_data(¶ms->q_size, ptr, sizeof(params->q_size)); 87 ptr = dh_unpack_data(¶ms->g_size, ptr, sizeof(params->g_size)); 88 if (secret.len != crypto_dh_key_len(params)) 89 return -EINVAL; 90 91 /* 92 * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since 93 * some drivers assume otherwise. 94 */ 95 if (params->key_size > params->p_size || 96 params->g_size > params->p_size || params->q_size > params->p_size) 97 return -EINVAL; 98 99 /* Don't allocate memory. Set pointers to data within 100 * the given buffer 101 */ 102 params->key = (void *)ptr; 103 params->p = (void *)(ptr + params->key_size); 104 params->q = (void *)(ptr + params->key_size + params->p_size); 105 params->g = (void *)(ptr + params->key_size + params->p_size + 106 params->q_size); 107 108 /* 109 * Don't permit 'p' to be 0. It's not a prime number, and it's subject 110 * to corner cases such as 'mod 0' being undefined or 111 * crypto_kpp_maxsize() returning 0. 112 */ 113 if (memchr_inv(params->p, 0, params->p_size) == NULL) 114 return -EINVAL; 115 116 /* It is permissible to not provide Q. */ 117 if (params->q_size == 0) 118 params->q = NULL; 119 120 return 0; 121 } 122 EXPORT_SYMBOL_GPL(crypto_dh_decode_key); 123